Wireless power transmission device for vehicle and wireless charging method

ABSTRACT

A wireless power transmission device for a vehicle and a wireless charging method are provided. The wireless charging method by the wireless power transmission device for a vehicle can comprise the steps of: transmitting a signal for detection of a wireless power reception device by using a lower frequency band than an operating frequency band used to control the vehicle; receiving a response signal for the transmitted signal and a power control signal from the wireless power reception device; controlling an operating frequency and/or a voltage in the wireless power transmission device for the vehicle according to the power control signal; and transmitting wireless power to the wireless power reception device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage of International Application No.PCT/KR2014/009186, filed Sep. 30, 2014, which claims the benefit ofpriority to U.S. Provisional Application No. 61/885,522, filed Oct. 2,2013, in the U.S. Patent and Trademark Office, the disclosures of whichare incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a wireless power transmission devicemounted on a vehicle and a wireless charging method.

Related Art

Recently, propagation of portable electronic devices including a smartphone, a laptop, a MP3 (MPEG-1 audio Layer-3) player, a headset, and thelike has been spread. However, since the portable electronic deviceoperates by consuming power stored in a battery cell (for example, aprimary battery, a secondary battery, and the like), the battery cellneeds to be charged or replaced in order to continuously operate theportable electronic device.

Methods of charging the battery cell are largely classified into acontact charging method of charging the battery cell by using a powersupply line and a power supply terminal and a non-contact chargingmethod of charging wireless power induced by a magnetic field generatedin a primary coil of a wireless power transmission device by using awireless power reception device. However, in the contact chargingmethod, when the charger and the battery are coupled with each other orseparated from each other, an instantaneous discharge phenomenon appearswhile different potentials are generated at both terminals. Since theterminal is exposed outside, the fire may occur when the foreignmaterial is filed in the terminal, and there are problems in that thebattery due to moisture is naturally discharged and the lifespan and theperformance of the battery are deteriorated. Accordingly, recently, thestudy on the non-contact charging method has been actively in progressin order to solve the aforementioned problems.

As one of techniques on the non-contact charging method, in “non-contactpoint charging system” in Korea Patent Registration No. 10-0971705, itis disclosed that when the load change is detected in a primary coreunit of a non-contact point power transmission device, a delay time froman output time of a request signal to a reception time of a responsesignal corresponding to the request signal and compared with a referencedelay time. Thereafter, when the measuring time is smaller than thereference standby time, the corresponding object is determined as theforeign material, and when the measuring time is larger than thereference standby time, the corresponding object is determined as anormal non-contact point power reception device and then the wirelesspower signal is transmitted.

The wireless power transmission system may be classified into a magneticinduced method and a resonance induced method. The magnetic induced typewireless power transmission system according to a wireless powerconsortium (WPC) standard is a system having a frequency characteristicset to 100 KHz and uses a frequency band of 110 KHz to 205 KHz.Meanwhile, an electro-magnetic compatibility (EMC) standard is managedbased on a frequency band of 150 KHz with respect to the vehicle. Forexample, the smart key controlling the vehicle uses 125 KHz as theoperation frequency. Accordingly, when the magnetic induced typewireless power transmission system is constructed in the vehicle, theinterference between the operation frequency of the wireless powertransmission system and the operation frequency controlling thecorresponding vehicle may occur. This causes malfunction of the wirelesspower transmission system and the vehicle. When the vehicle ismalfunctioned, a large accident may occur. Therefore, a wireless powertransmission device for a vehicle and a wireless charging method, whichare compatible with the existing wireless power transmission systemwhile avoiding an interference frequency with the electronic devicesprovided in the vehicle, are required.

SUMMARY OF THE INVENTION

The present invention provides a wireless power transmission device fora vehicle and a wireless charging method capable of avoiding a frequencyinterference with electronic devices provided in a vehicle.

The present invention also provides a wireless power transmission devicefor a vehicle compatible with an existing wireless power transmissionsystem and a wireless charging method.

In an aspect, a wireless charging method by a wireless powertransmission device for a vehicle is provided. The method includestransmitting a signal for detecting a wireless power reception device byusing a frequency band lower than an operation frequency band used incontrol of the vehicle, receiving a response signal for the transmittedsignal and a power control signal from the wireless power receptiondevice, controlling at least one of an operation frequency and voltagein the wireless power transmission device for the vehicle, andtransmitting wireless power to the wireless power reception device.

As an example, the operation frequency band used in the control of thevehicle may include an operation frequency band of a smart key.

As another example, the resonance frequency of the wireless powertransmission device for the vehicle may be lower than the resonancefrequency of the wireless power reception device.

As yet another example, the resonance frequency of the wireless powertransmission device for the vehicle and the resonance frequency of thewireless power reception device may be different from each other.

As still another example, the resonance frequency of the wireless powertransmission device for the vehicle may be higher than the resonancefrequency of the wireless power reception device.

As still yet another example, the controlling may include setting theoperation frequency to a higher frequency in the frequency band, whenthe power control signal indicates an increase in the wireless power.

As still yet another example, the controlling may include setting theoperation frequency to a lower frequency in the frequency band, when thepower control signal indicates a decrease in the wireless power.

In another aspect, a wireless power transmission device for a vehicle isprovided. The wireless power transmission device includes a primary coiltransmitting a signal for detecting a wireless power reception deviceand a power signal by using a frequency band lower than an operationfrequency band used in control of the vehicle, an electric driving unitconnected to the primary coil to apply an electric driving signal to theprimary coil so that an electromagnetic is generated, and a control unitcontrolling at least one of the operation frequency of the wirelesspower transmission device for the vehicle and the voltage in thewireless power transmission device for the vehicle according to thepower control signal received from the wireless power reception device.

The wireless power transmission device for the vehicle can avoidfrequency interference between the electronic devices provided in thevehicle like the smart key when performing the wireless charging andhave compatibility with an existing wireless power transmission system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a series resonance curve for wirelesspower transmission.

FIG. 2 is a diagram for describing a frequency band using in a wirelesspower transmission system.

FIG. 3 is a flowchart illustrating a wireless charging method of awireless power transmission device for a vehicle according to anexemplary embodiment of the present invention.

FIG. 4 is a diagram for describing a power control method of a generalwireless power transmission device.

FIG. 5 is a diagram for describing a power control method of a wirelesspower transmission device according to another exemplary embodiment ofthe present invention.

FIG. 6 is a diagram illustrating a wireless power transmission system towhich the present invention is applied.

FIG. 7 is a block diagram illustrating a wireless power transmissiondevice for a vehicle according to yet another exemplary embodiment ofthe present invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present invention will be described more fully hereinafter withreference to the accompanying drawings, in which exemplary embodimentsof the invention are shown. As those skilled in the art would realize,the described embodiments may be modified in various different ways, allwithout departing from the spirit or scope of the present invention.Parts which are not related with the description are omitted in order toclearly describe the present invention in the drawings and likereference numerals designate like elements throughout the specification.

Throughout the specification, unless explicitly described to thecontrary, the word “comprise” and variations such as “comprises” or“comprising”, will be understood to imply the inclusion of statedelements but not the exclusion of any other elements. In addition, theterms “unit” described in the specification mean units for processing atleast one function and operation and can be implemented by hardwarecomponents or software components and combinations thereof.

The term “wireless power” used in this specification means any form ofenergy related with an electric field, a magnetic field, anelectromagnetic field, and the like which are transmitted from atransmitter to a receiver without using physical electromagneticconductors. Wireless power may also be called a power signal and mean anoscillating magnetic flux vibrating while being enclosed by a primarycoil of a transmission side and a secondary coil of a reception side.Hereinafter, power conversion in a wireless power transmission systemfor wirelessly charging wireless power devices including a mobile phone,a cordless phone, a smart phone, an MP3 player, a laptop, a headset, andthe like will be described as an example. A basic principle of wirelesspower transmission includes both a magnetic induced coupling method anda magnetic resonance coupling (that is, resonance induction) methodusing frequencies having less than 30 MHz. However, in relatively highradiation levels, for example, various frequencies including frequenciesin which a license-exempt operation in less than 135 kHz (LF) or 13.56MHz (HF) is allowed may be used.

FIG. 1 is a diagram illustrating a series resonance curve for wirelesspower transmission, and FIG. 2 is a diagram for describing a frequencyband using in a wireless power transmission system.

A wireless power transmission system operates by using aright-directional frequency band (that is, a frequency band higher thana resonance frequency) of a resonance frequency f_(o) in a seriesresonance curve as illustrated in FIG. 1. In an LC series resonancestructure, the resonance frequency fo is set based on the followingEquation 1.

$\begin{matrix}{f_{0} = \frac{1}{2\;\pi\sqrt{LC}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

In this case, the transmission side controls transmission power bylifting up or down an operation frequency toward the resonance frequencyf_(o), according to a value of a power compensation signal received froma reception side.

Meanwhile, a difference between resonance frequencies at points where 3dB, that is, a current value is reduced by half to both sides based onthe resonance frequency is referred to as a 3 dB bandwidth, and a valueobtained by dividing the resonance frequency f_(o) by 3 dB is a Q value.Accordingly, as illustrated in FIG. 2, as a resonance characteristic issharper, the 3 dB bandwidth is decreased and the Q value is increased(High Q). Therefore, in a circuit, a circuit Q value is related with thebandwidth. That is, when the Q value of the circuit is low, it is meantthat the bandwidth is wide, and when the Q value is high, it is meantthat the bandwidth is narrow. Herein, the resonance means a selectivecharacteristic of a specific frequency. Selecting sharply the frequencyeventually means increasing the Q value. In the case where the narrowfrequency band is fixedly required, the Q value needs to be high. On thecontrary, when the used frequency band is wide, the Q value needs to below. Accordingly, when the wireless power transmission system isdesigned, it is important how much the selection degree and thebandwidth are required, and the selection degree and the bandwidth aredetermined by the Q value. Therefore, the wireless power transmissionsystem according to the present invention may widely use the frequencyband by using the resonance in which the Q value is low.

FIG. 3 is a flowchart illustrating a wireless charging method of awireless power transmission device for a vehicle according to anexemplary embodiment of the present invention.

The wireless power transmission device for the vehicle according to thepresent invention may perform a process illustrated in FIG. 3 forcharging a battery cell as an example. Herein, the battery cell may beincluded in the portable electronic device and connected or included to(in) a wireless power reception device. For example, the wireless powertransmission device for the vehicle according to the present inventionmay be included in the vehicle, and in this case, the portableelectronic device may charge the battery cell by using the wirelesspower reception device in the vehicle.

Referring to FIG. 3, the wireless power transmission device for thevehicle transmits a signal for detecting the wireless power receptiondevice by using a lower frequency band than the operation frequencycontrolling the vehicle (S310). For example, the operation frequencyband controlling the vehicle may include an operation frequency band ofa smart key. Further, the smart key may operate at a frequency of 125KHz, and the wireless power transmission device for the vehicle may usea frequency band of 90 to 110 KHz.

Meanwhile, the wireless power transmission device for the vehicle mayperform wireless charging by using a lower frequency band than theresonance frequency set in the wireless power transmission device forthe vehicle. The resonance frequency in the wireless power transmissiondevice for the vehicle according to the present invention may bedifferent from the resonance frequency in the wireless power receptiondevice. As an example, the resonance frequency in the wireless powertransmission device for the vehicle may be set to be higher than theresonance frequency of 100 KHz in the wireless power reception device.

Further, the signal for detecting the wireless power reception devicemay be a digital ping. In the digital ping, the wireless power receptiondevice may transmit required information to the wireless powertransmission device, and the wireless power transmission device for thevehicle according to the present invention may receive a response signalfor the digital ping, a power control signal, and the like from thewireless power reception device by using the frequency band (S320). Forexample, when the wireless power reception device receives the digitalping from the wireless power transmission device, the wireless powerreception device may transmit information on a unique identifier (ID), amanufacturer ID, and the like of the wireless power reception device tothe wireless power transmission device by using load modulation.Further, the wireless power reception device may transmit power controlinformation of requesting for controlling a level of wireless powerreceived from the wireless power transmission device, charging stateinformation of representing a charged level of the battery cell,full-charging information of notifying that the battery cell is fullycharged, signal intensity information for determining a primary coil forpower transmission at the transmission side, rectified power informationrepresenting an amount of the power supplied to output, and the like,through the load modulation. Even though an object is detected throughthe digital ping, when the unique ID, the manufacturer ID, and the likeof the wireless power reception device are not received, the wirelesspower transmission device for the vehicle according to the presentinvention may determine the corresponding object as a foreign object.When the detected object is determined as the foreign object, thewireless power transmission device for the vehicle does not transmit thewireless power. When the detected object is identified as the wirelesspower reception device, the wireless power transmission device for thevehicle may start the wireless power transmission.

Meanwhile, when the power control signal is received from the wirelesspower reception device while transmitting the wireless power, thewireless power transmission device for the vehicle may control at leastone of the operation frequency of the wireless power transmission devicefor the vehicle and voltage in the wireless power transmission devicefor the vehicle according to the power control signal (S330). Forexample, when the power control signal indicates an increase in thewireless power, that is, the wireless power reception device requestsmore power to be transmitted, the wireless power transmission device forthe vehicle may set the operation frequency as a higher frequency in thefrequency band set in the wireless power transmission device for thevehicle. On the contrary, when the power control signal indicates adecrease in the wireless power, the wireless power transmission devicefor the vehicle may set the operation frequency as a lower frequency inthe frequency band. Thereafter, the wireless power transmission devicefor the vehicle may transmit the wireless power controlled according tothe power control signal based on the frequency control and/or powercontrol to the corresponding wireless power reception device (S340).

FIG. 4 is a diagram for describing a power control method of a generalwireless power transmission device, and FIG. 5 is a diagram fordescribing a power control method of a wireless power transmissiondevice according to another exemplary embodiment of the presentinvention. Hereinafter, a power control method of a wireless powertransmission device according to the present invention will be describedin more detail with reference to FIGS. 4 and 5.

First, referring to FIG. 4, a general wireless power transmission deviceuses the resonance frequency F_(o) of 100 KHz like the wireless powerreception device and controls the operation frequency to a maximumcurrent frequency F1 when largely transmitting the power and to aminimum current frequency F2 when less transmitting the power. In thiscase, the maximum current frequency F1 may be 110 KHz and the minimumcurrent frequency F2 may be 205 KHz (F1<F2). That is, the frequency bandused in the wireless power transmission device may be 110 KHz to 205KHz. However, when the frequency band used in the general wireless powertransmission device is used as it is in the vehicle, interferencebetween the frequency used in the general wireless power transmissiondevice and the frequency used in electronic devices provided in thevehicle may occur. Particularly, since a smart key controlling thevehicle may use 125 KHz as the operation frequency, when the generalwireless power transmission device is used in the vehicle, the vehiclemalfunctions by the interference between the operation frequency of thesmart key and the operation frequency of the general wireless powertransmission device. Accordingly, the wireless power transmission devicefor the vehicle according to the present invention may use a leftfrequency band (a lower frequency band than the resonance frequency ofthe wireless power transmission device for the vehicle) based on aresonance frequency F′_(o) of the wireless power transmission device forthe vehicle as illustrated in FIG. 5. Further, because the used(alternatively, operation) frequency band is narrow, voltage control maybe used together if necessary. As an example, the wireless powertransmission device for the vehicle according to the present inventionmay use the frequency band of 90 KHz to 110 KHz. However, in this case,position of the maximum current frequency F1 and position of the minimumcurrent frequency F2 are reversed based on the resonance frequency F_(o)of the wireless power reception device (F2<F1). Accordingly, in F2 toF_(o), that is, in the case where the operation frequency is lower thanF_(o), when the same frequency control (frequency decrease) as theexisting frequency is performed with respect to a positive signal (asignal to more transmit the power) transmitted by the wireless powerreception device, the reception power of the wireless power receptiondevice is decreased, and thus, the wireless power transmission devicefor the vehicle reversely performs the frequency control to the existingfrequency. That is, the wireless power transmission device for thevehicle according to the present invention may set the operationfrequency to be increased to the resonance frequency F′_(o) with respectto additional power demand wireless power reception device when theoperation frequency is set between F2 to F_(o). On the contrary, withrespect to power decrease demand of the wireless power reception device,the operation frequency may be set to the minimum current frequency F2.Due to such an operation, the wireless power transmission device for thevehicle according to the present invention is compatible with thegeneral wireless power reception device.

FIG. 6 is a diagram illustrating a wireless power transmission system towhich the present invention is applied.

Referring to FIG. 6, a wireless power transmission system 600 includes awireless power transmission device 610 and one wireless power receptiondevice 650-1 or n (herein, n is a natural number) wireless powertransmission devices 650-1, . . . , 650-n. The wireless powertransmission device 610 may be the wireless power transmission devicefor the vehicle.

The wireless power transmission device 610 includes a primary core. Theprimary core may include one or more primary coils. The wireless powertransmission device 610 may have any suitable form, but one preferableform may be a flat platform having a power transmission surface. Therespective wireless power reception devices 650-1, . . . , 650-n may bepositioned on the platform or near the platform.

Each of the wireless power reception devices 650-1, . . . , 650-n may beseparated from the wireless power transmission device 610. When each ofthe wireless power reception devices 650-1, . . . , 650-n is positionednear the wireless power transmission device 610, each of the wirelesspower reception devices 650-1, . . . , 650-n includes a secondary corecoupled with an electromagnetic field generated by the primary core ofthe wireless power transmission device 610. The secondary core mayinclude one or more secondary coils.

The wireless power transmission device 610 transmits the power to thewireless power reception devices 650-1, . . . , 650-n without directelectric contact. In this case, the primary core and the secondary coreare magnetic induced-coupled or resonance-induced coupled with eachother. The primary coil or the secondary coil may have any suitableforms. As an example, the primary core and the secondary core may becopper coils wound around a formation having high permeability such asferrite or amorphous material.

The wireless power reception devices 650-1, . . . , 650-n are connectedto an external load (not illustrated, herein, also referred to as anactual load of the wireless power reception device) to supply the powerwirelessly received from the wireless power transmission device 610 tothe external load. For example, the wireless power reception devices650-1, . . . , 650-n may carry the received power to an object whichconsumes or stores the power, like a portable electric or electronicdevice or a rechargeable battery cell or cell, respectively.

FIG. 7 is a block diagram illustrating a wireless power transmissiondevice for a vehicle according to yet another exemplary embodiment ofthe present invention.

Referring to FIG. 7, a wireless power transmission device 700 for avehicle includes a primary coil 710, an electric driving unit 720, acontrol unit 730, and a current measuring unit 740.

The primary coil 710 transmits a detecting signal of the wireless powerreception device and a power signal by using a frequency band lower thanan operation frequency band of a smart key.

The electric driving unit 720 is connected to the primary coil 710 toapply electric driving signals to the primary coil 710 so that theelectromagnetic field is generated in the primary coil 710.

The control unit 730 is connected to the electric driving unit 720 togenerate a control signal 731 that controls an alternating current (AC)signal required when the primary coil 710 generates an induced magneticfield or magnetic resonance. The control unit 730 may control at leastone of the operation frequency and the voltage in the wireless powertransmission device according to the power control signal received fromthe wireless power reception device.

The current measuring unit 740 measures current flowing in the primarycoil 710. The current measured by the current measuring unit 740 may beAC. As an example, the current measuring unit 740 may be a currentsensor. Alternatively, the current measuring unit 740 may be atransformer which lowers and uses high current flowing in the primarycoil to low current.

The control unit 730 may obtain information transmitted by the wirelesspower reception device by using the current value measured in thecurrent measuring unit 740. Until the demand power is satisfied bychanging the load, the wireless power reception device maycontinuously/periodically transmit the power control signal requestingthe power increase or the power control signal requesting the powerdecrease to the wireless power transmission device 700 for the vehicle.For example, when the control unit 730 receives the power control signalrequesting the power increase from the wireless power reception devicethrough the load change, the intensity of the current flowing in theprimary coil 710 may increase so that higher power is transmitted as theresponse thereto. In more detail, the control unit 730 may adjust thecontrol signal 731 so that an AC signal larger than a reference ACsignal may be applied to the primary coil 710 in order that largercurrent flows in the primary coil 710. On the contrary, when the controlunit 730 receives the power control signal requesting the power decreasefrom the wireless power reception device, the control signal 731 may beadjusted so that the AC signal lower than the reference AC signal may beapplied to the primary coil 710 in order that the power lower than thecurrent transmission power is transmitted.

Further, when the operation frequency of the wireless power transmissiondevice for the vehicle is lower than the resonance frequency of thewireless power reception device, in order to transmit larger wirelesspower through the primary coil 710, the control unit 730 may set theoperation frequency to a higher frequency in the operation frequencyband of the wireless power transmission device 700 for the vehicle. Onthe contrary, when the operation frequency of the wireless powertransmission device for the vehicle is lower than the resonancefrequency of the wireless power reception device, in order to transmitlower wireless power through the primary coil 710, the control unit 730may set the operation frequency to a lower frequency in the operationfrequency band of the wireless power transmission device 700.

Meanwhile, even though the operation frequency of the wireless powertransmission device for the vehicle is the same as the resonancefrequency of the wireless power reception device, when the wirelesspower reception device requires the power increase, the control unit 730may adjust the control signal 731 so that the AC signal larger than thereference AC signal may be applied to the primary coil 710. On thecontrary, even though the operation frequency of the wireless powertransmission device for the vehicle is the same as F1 or F2, when thewireless power reception device requires the power decrease, the controlunit 730 may adjust the control signal 731 so that the AC signal lowerthan the reference AC signal may be applied to the primary coil 710. Aseries of the aforementioned process is collectively referred to as apower control.

The primary coil 710 may transmit the wireless power controlled by thecontrol unit 730 to the wireless power reception device according to thepower control signal received from the wireless power reception device.

Meanwhile, even though illustrated in FIG. 7, the wire powertransmission device for the vehicle according to the present inventionmay include a shield member for protecting the wireless powertransmission device for the vehicle from a stray magnetic field or aneddy current.

Further, the wireless power transmission device for the vehicleaccording to the present invention may include a temperature protectioncircuit of monitoring the temperature around the interface. When thetemperature measured by the temperature protection circuit is more thata threshold value, the wireless power transmission device for thevehicle according to the present invention may stop or end the powertransmission for safety.

The above description just illustrates the technical spirit of thepresent invention and various modifications and transformations can bemade by those skilled in the art without departing from an essentialcharacteristic of the present invention. Accordingly, the variousembodiments disclosed herein are not intended to limit the technicalspirit but describe with the true scope and spirit being indicated bythe following claims. The scope of the present invention should beinterpreted by the appended claims and all technical spirit in theequivalent range thereto should be interpreted to be embraced by theclaims of the present invention.

What is claimed is:
 1. A wireless charging method performed by awireless power transmission device for use in a vehicle, the methodcomprising: transmitting, from the wireless power transmission device, adetecting signal for detecting a wireless power reception device,wherein the detecting signal is in a frequency band that is differentthan an operation frequency band used in control of the vehicle;receiving a response signal and a power control signal from the wirelesspower reception device in response to the detecting signal; controllingat least one of a power signal frequency or a voltage of wireless powerproduced by the wireless power transmission device according to thepower control signal; and transmitting the wireless power to thewireless power reception device, wherein the controlling includesadjusting the power signal frequency of the wireless power based, atleast in part, on a resonance frequency of the wireless power receptiondevice and different than the operation frequency band used in controlof the vehicle.
 2. The wireless charging method of claim 1, wherein theoperation frequency band used in the control of the vehicle includes anoperation frequency band of a smart key.
 3. The wireless charging methodof claim 1, wherein the power signal frequency of the wireless powerproduced by the wireless power transmission device and the resonancefrequency of the wireless power reception device are different from eachother.
 4. The wireless charging method of claim 3, wherein the powersignal frequency of the wireless power produced by the wireless powertransmission device is higher than the resonance frequency of thewireless power reception device.
 5. The wireless charging method ofclaim 1, wherein the controlling includes: setting the power signalfrequency to a higher frequency when the power control signal indicatesa request for an increase in the wireless power and the power signalfrequency is lower than the resonance frequency of the wireless powerreception device; and setting the power signal frequency to a lowerfrequency when the power control signal indicates a request for anincrease in the wireless power and the power signal frequency is higherthan the resonance frequency of the wireless power reception device. 6.The wireless charging method of claim 1, wherein the controllingincludes: setting the power signal frequency to a lower frequency whenthe power control signal indicates a request for a decrease in thewireless power and the power signal frequency is lower than theresonance frequency of the wireless power reception device; and settingthe power signal frequency to a higher frequency when the power controlsignal indicates a request for a decrease in the wireless power and thepower signal frequency is higher than the resonance frequency of thewireless power reception device.
 7. A wireless power transmission devicefor use in a vehicle comprising: a primary coil configured to transmit adetecting signal for detecting a wireless power reception device,wherein the detecting signal is in a frequency band that is differentthan an operation frequency band used in control of the vehicle; theprimary coil configured to receive a response signal and a power controlsignal from the wireless power reception device in response to thedetecting signal; the primary coil configured to produce wireless powerfor the wireless power reception device; and a control unit configuredto control at least one of a power signal frequency or a voltage of thewireless power produced by the wireless power transmission deviceaccording to the power control signal, wherein the control unit isfurther configured to adjust the power signal frequency of the wirelesspower based, at least in part, on a resonance frequency of the wirelesspower reception device and different than the operation frequency bandused in control of the vehicle.
 8. The wireless power transmissiondevice of claim 7, wherein the operation frequency band used in thecontrol of the vehicle includes an operation frequency band of a smartkey.
 9. The wireless power transmission device of claim 7, wherein thepower signal frequency of the wireless power produced by the wirelesspower transmission device and the resonance frequency of the wirelesspower reception device are different from each other.
 10. The wirelesspower transmission device of claim 9, wherein the power signal frequencyof the wireless power produced by the wireless power transmission deviceis higher than the resonance frequency of the wireless power receptiondevice.
 11. The wireless power transmission device of claim 7, whereinthe control unit sets the power signal frequency to a higher frequencywhen the power control signal indicates a request for an increase in thewireless power and the power signal frequency is lower than theresonance frequency of the wireless power reception device, and whereinthe control unit sets the power signal frequency to a lower frequencywhen the power control signal indicates a request for an increase in thewireless power and the power signal frequency is higher than theresonance frequency of the wireless power reception device.
 12. Thewireless power transmission device of claim 7, wherein the control unitsets the power signal frequency to a lower frequency when the powercontrol signal indicates a request for a decrease in the wireless powerand the power signal frequency is lower than the resonance frequency ofthe wireless power reception device, and wherein the control unit setsthe power signal frequency to a higher frequency when the power controlsignal indicates a request for a decrease in the wireless power and thepower signal frequency is higher than the resonance frequency of thewireless power reception device.
 13. The method of claim 1, wherein thecontrolling includes: adjusting the power signal frequency to a higherfrequency or a lower frequency based on the power control signal,wherein the power signal frequency is adjusted in a first direction whenthe power signal frequency is lower than the resonance frequency of thewireless power reception device, and wherein the power signal frequencyis adjusted in a second direction that is reverse of the first directionwhen the power signal frequency is higher than the resonance frequencyof the wireless power reception device.